A liquid crystal display device based on a technology called IPS has a pair of transparent substrates disposed facing each other through a liquid crystal. Each pixel region of one of the transparent substrates closer to the liquid crystal has a pixel electrode; and a common electrode for generating an electric field (lateral electric field) parallel to the transparent substrates, between the pixel electrode and the common electrode. The amount of light transmitting through a region between the pixel electrode and the common electrode is regulated by controlling driving the liquid crystal according to an electric field. Such a liquid crystal display device is known as being capable of providing unchanged display images even if viewed from a diagonal direction with respect to the screen surface (excellent in so-called wide viewing angle characteristics).
Conventionally, in such a liquid crystal display device, a pixel electrode and a common electrode have been formed of a conductive layer that does not transmit light. In recent years, however, the following type has been known. That is, common electrodes made of transparent electrodes are formed on the entire area of the region excluding around the pixel regions, and strip-shaped pixel electrodes are formed on the common electrodes through an insulating film.
With a liquid crystal display device thus structured, a lateral electric field is generated between a pixel electrode and a common electrode, which provides excellent wide viewing angle characteristics and a higher aperture ratio (refer to patent literature 1 for example).
Meanwhile, a liquid crystal display device with the diagonal electric field method has been developed. In the device, pixel electrodes and common electrodes for applying an electric field to the liquid crystal layer are disposed on different layers through an insulating film. The device provides a wider viewing angle and a higher contrast than the IPS method, and further the device can be driven at low voltage and has a high transmittance, thereby featuring bright display.
However, the device involves the following problems. That is, the potential difference between a drain signal line and a pixel electrode causes orientation misalignment, which produces a region that does not contribute to display near a signal line to decrease the aperture ratio. Further, coupling capacitance produced between a signal line and a pixel electrode likely degrades display quality (e.g. crosstalk).
Hence, a liquid crystal display device is devised in which pixel electrodes and common electrodes are disposed on an interlayer resin film in order to reduce such influence by potential of a signal line (refer to patent literatures 2 and 3 for example).
However, a request has been made for providing a liquid crystal display device with a higher aperture ratio (transmittance) and a method of manufacturing the device at low cost.